A typical electrical trolley bus vehicle includes propulsion equipment and auxiliary load devices that draw current from a power source trolley wire through pickup devices carried by the vehicle. The auxiliary load devices can include load voltage equipment such as the lights, blowers, air conditioners, heaters, and so forth of the trolley bus.
It is known to provide a DC-to-DC voltage converter for a trolley bus operation which is coupled with the input DC trolley wire energized by a well known power supply that nominally is 600 volts DC but can vary from 300 volts DC to 800 volts DC. THe DC-to-DC voltage converter apparatus can provide a regulated DC output determined by controlling the ON and OFF ratio of operation of a thyristor inverter circuit on the primary of a transformer with the secondary of that transformer being coupled to the output load through a full wave rectifier and a filter circuit. If two separate and independent regulated power supplies are provided to supply current to the propulsion equipment and to the auxiiiary load devices, this involves considerable expense and requires additional space on the trolley bus.